From 46e129be7445608d58057a6e2cb2d5a487dee250 Mon Sep 17 00:00:00 2001
From: Paul Jensen <pauljensen@google.com>
Date: Tue, 5 Aug 2014 14:13:48 -0400
Subject: [PATCH] Avoid reusing a currently active NetID.

There are only a limited number (65526) of NetIDs so the chance for reusing
one exists.  Reusing a currently active NetID will cause problems like netd
failures and overwriting entries in mNetworkForNetId.

bug:16815182

Change-Id: Ib75302beae3179c3f3b90c345cf4d2cf5f4ad2be
---
 .../android/server/ConnectivityService.java   | 24 ++++++++++++-------
 .../server/connectivity/NetworkAgentInfo.java |  9 +++----
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index 67c01e50bb..8354137142 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -756,10 +756,20 @@ public class ConnectivityService extends IConnectivityManager.Stub {
         return mNextNetworkRequestId++;
     }
 
-    private synchronized int nextNetId() {
-        int netId = mNextNetId;
-        if (++mNextNetId > MAX_NET_ID) mNextNetId = MIN_NET_ID;
-        return netId;
+    private void assignNextNetId(NetworkAgentInfo nai) {
+        synchronized (mNetworkForNetId) {
+            for (int i = MIN_NET_ID; i <= MAX_NET_ID; i++) {
+                int netId = mNextNetId;
+                if (++mNextNetId > MAX_NET_ID) mNextNetId = MIN_NET_ID;
+                // Make sure NetID unused.  http://b/16815182
+                if (mNetworkForNetId.get(netId) == null) {
+                    nai.network = new Network(netId);
+                    mNetworkForNetId.put(netId, nai);
+                    return;
+                }
+            }
+        }
+        throw new IllegalStateException("No free netIds");
     }
 
     private int getConnectivityChangeDelay() {
@@ -4104,7 +4114,7 @@ public class ConnectivityService extends IConnectivityManager.Stub {
             int currentScore, NetworkMisc networkMisc) {
         enforceConnectivityInternalPermission();
 
-        NetworkAgentInfo nai = new NetworkAgentInfo(messenger, new AsyncChannel(), nextNetId(),
+        NetworkAgentInfo nai = new NetworkAgentInfo(messenger, new AsyncChannel(),
             new NetworkInfo(networkInfo), new LinkProperties(linkProperties),
             new NetworkCapabilities(networkCapabilities), currentScore, mContext, mTrackerHandler,
             networkMisc);
@@ -4118,9 +4128,7 @@ public class ConnectivityService extends IConnectivityManager.Stub {
     private void handleRegisterNetworkAgent(NetworkAgentInfo na) {
         if (VDBG) log("Got NetworkAgent Messenger");
         mNetworkAgentInfos.put(na.messenger, na);
-        synchronized (mNetworkForNetId) {
-            mNetworkForNetId.put(na.network.netId, na);
-        }
+        assignNextNetId(na);
         na.asyncChannel.connect(mContext, mTrackerHandler, na.messenger);
         NetworkInfo networkInfo = na.networkInfo;
         na.networkInfo = null;
diff --git a/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java b/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
index 4eb2ef1c34..5a97aee972 100644
--- a/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
+++ b/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
@@ -40,7 +40,7 @@ import java.util.ArrayList;
  */
 public class NetworkAgentInfo {
     public NetworkInfo networkInfo;
-    public final Network network;
+    public Network network;
     public LinkProperties linkProperties;
     public NetworkCapabilities networkCapabilities;
     public int currentScore;
@@ -55,12 +55,12 @@ public class NetworkAgentInfo {
     public final Messenger messenger;
     public final AsyncChannel asyncChannel;
 
-    public NetworkAgentInfo(Messenger messenger, AsyncChannel ac, int netId, NetworkInfo info,
+    public NetworkAgentInfo(Messenger messenger, AsyncChannel ac, NetworkInfo info,
             LinkProperties lp, NetworkCapabilities nc, int score, Context context, Handler handler,
             NetworkMisc misc) {
         this.messenger = messenger;
         asyncChannel = ac;
-        network = new Network(netId);
+        network = null;
         networkInfo = info;
         linkProperties = lp;
         networkCapabilities = nc;
@@ -87,6 +87,7 @@ public class NetworkAgentInfo {
 
     public String name() {
         return "NetworkAgentInfo [" + networkInfo.getTypeName() + " (" +
-                networkInfo.getSubtypeName() + ") - " + network.toString() + "]";
+                networkInfo.getSubtypeName() + ") - " +
+                (network == null ? "null" : network.toString()) + "]";
     }
 }